Evaluation of concrete water content and other durability indicators by electromagnetic measurements

In order to use non destructive techniques (NDT) for the survey of reinforced concrete structures, it is important to show their ability to measure the cover concrete characteristics related to durability, in particular the concrete water and chloride contents. For this purpose, tests with two electromagnetic methods (GPR and capacitive probes) and impact echo method were carried out on 81 slabs of 9 different concrete mixes. Concrete porosity was ranging between 12.5 and 18%. Measurements were carried out at five different water contents. A real structure was also tested in situ. The NDT results are compared to concrete performance indicators such as porosity and water content, as well as chloride profiles. The comparisons show the complementarity of the methods to perform a pertinent diagnosis of concrete structures.